At present different solutions exist in order to step-up or step-down a DC voltage to another DC voltage.
In most DC-DC converters according to known technology, the conversion of DC voltages is achieved by using a power inductor and a capacitor.
One known example of such a DC-DC converter is given in FIG. 1.
A similar principle of use for the inductor as an energy storage device is disclosed in the U.S. Pat. No. 5,729,562, where a high voltage pulse power generating circuit is realized by means of a voltage storing element coupled to an energy recovery circuit which reverses the polarity of the energy dissipated by the pulse generation circuit and delivers this energy back to the power source. However, the circuit disclosed in U.S. Pat. No. 5,579,562 is not a DC-DC converter.
The main disadvantage of using discrete inductors as energy storage devices is the difficulty in providing them in high frequency microwave circuits. One other disadvantage of using lumped components for energy storage is their inability to be used in DC-DC converters integrated on a chip. Moreover, discrete power inductors are often the most bulky and expensive component in DC-DC converters.
One other example of a DC-DC converter is illustrated in the article by S. Djukic, et al. “A Planar 4.5-GHz DC-DC Power Converter”, IEEE Transactions on Microwave Theory and Techniques, Vol. 47, No. 8, August 1999, where it is attempted to realize a power converter operating at microwave frequencies by using a class-E amplifier and Schottky diodes as rectifiers. The class-E amplifier consists of a transistor used as a switch and microstrip transmission lines acting as output capacitances and inductances. Even though the paper states that discrete components for DC-DC power conversion were not used, inductors as energy storages devices are nevertheless used for the gate and drain voltages of the power amplifier.
U.S. Pat. No. 6,946,868 attempts at using the transmission line with a switch operated to switch the input voltage through a transmission line in order to deliver an output voltage to a load without ringing in the output voltage. This is achieved by stepping up the input voltage several times and by performing the switching from one voltage level to the next at the time a reflected voltage wave arrives at the input of the transmission line.
While in this case the output voltage to the load more closely follows the input voltage sent through the transmission line avoiding ringing in the output voltage, a DC up- or down-conversion of the input voltage is neither achieved nor is the goal of the circuit disclosed.
One other solution for using a transmission line as an energy storage facility disclosed in the Dutch patent application NL7311616, where a high voltage pulse generator and two transmission lines in spiral form are used to store high voltage charges and where reflections of the voltage waves from the open ends of both transmission lines lead to a higher output voltage than the input voltage. This high output voltage is used to charge a load in the form of an X-ray tube.
The object of the invention is therefore to obviate at least some of the disadvantages with known technology.